https://blogs.lse.ac.uk/brexit/2019/12/03/a-missed-opportunity-revisiting-the-euro-referendum-that-never-was-from-a-historical-perspective/
https://www.consilium.europa.eu/media/54923/peg-letter-to-pec-march2022-signed.pdf
https://www.bruegel.org/sites/default/files/2022-11/PC%2020%202022_4.pdf